A proposal to investigate the application of numerical and optical image processing techniques to nuclear medical imaging to yield three-dimensional, quantitatively accurate images of radionuclide spatial distributions. Preliminary studies have demonstrated that already proven radiographic (transmission) transverse tomographic techniques are applicable to emission (i.e. radionuclide) tomography with appropriate alterations in data gathering equipment. We have also demonstrated by computer simulation that these techniques can be extended to yield three-dimensional images (in essence a set of serial tomographic sections). By combining the transmission and emission techniques it appears possible to generate a three-dimensional distribution image corrected for internal absorption, i.e. a quantitative spatial image. Preliminary technical and theoretical studies indicate that such a system could be developed around an unmodified Anger camera and available digital image processing systems to yield images with clinically useful resolution (2 - 3 cm). The necessary image processing appears impractical with the usual on-line minicomputer used in Nuclear Medicine due to the size of the computation required. Digital techniques will be developed using a large off-line computer. In addition, optical processing methods with be investigated in parallel on the premise that a combined. In addition, optical processing methods will be investigated in parallel on the premise that a combined digital-optical approach may represent the best answer to an economically feasible, clinically useful system.